Contents

Tagging

A single building outline can be created for each building complex or 'block', which may relate to a single detached property, or to a row of individual terraced houses or to some more complex arrangement of properties. It is however better to create a series of linked outlines which share some nodes at the boundary to identify each distinct part of the property.

In addition outlines can either be simplified shapes or very outlines which conform very accurately to the shape of the building. It is not uncommon for buildings to initially be described as simple group outlines later be improved with more detailed outlines and to be split into individual properties.

The address of the building can also be added. This can either be attached to the building outline, or more usefully to the appropriate main entrance which should have a node tagged with entrance=yes or entrance=*.

For larger public building with many entrances for different purposes and for us by different people the building entrance can also be tagged with a access=*. A building entrance can be connected to a description of the footpath access to the entrance by highway=footway and highway=steps etc. Where appropriate multiple entrances can have appropriate postal addresses.

Mentionable usage

There are structures tagged as buildings which are missing a foundation or are even moveable. For example many mappers are using the key building=* to describe moveable objects and buildings for example building=static_caravan, building=houseboat or trailers. While houseboats (often self propelled) or ships (for example museum or theatre ships) may be moved once, there are also building=floating_homes which are built on floating logs and do net get moved.

Differing from the ideal of mapping the outline of a building on the ground, many objects with building=* include parts of buildings (for example constructed on piers) which are only covering areas. building=roof and building=bridge even describe buildings which have, except its piers, no outline on the ground. The same holds for underground buildings like building=cellar or those building types which are tagged with location=underground.

Don't tag for the renderer

Some mappers are trying to modify OSM data to be rendered (e. g. by Mapnik) in a way to fit their wishes by creatively reinterpreting some existing tags.

Please map all attributes as close to the reality as possible with the available data. Make use of the descriptions for the tags at the refering wikipage. Use the existing values by its definition at the wiki and choose the best fitting pair of key and value. If there is no fitting tag and no more generic tag, you may find some uncommented already used tags at taginfo. If all of this does not suffice, you may better create a new tagging and document it at the wiki.

Here are some negative examples in context to buildings.

tagging of non existing amenity=* to emphasize the building at the rendered picture

modify/omit tagging due to dissatisfaction (e.g. cafe/restaurant)

building parts as distinct objects to structure the rendered picture

deleting/moving objects to obtain a (nicer) placement of the icon

tagging statues, bridge piers, gravestones, sockets, ships as buildings to make them visible on the map. This can be counterproductive even for 3D-Mapping.

Such manipulations damage not only the OSM, but also they are needless, because their effect is usually limited to a single renderer, which will be probably modified soon.

If there are substantial rendering errors, please contact the developers of the renderers directly.

How to map

When tracing from aerial imagery try to estimate the place where the building position on the ground which may be offset from the roof-line as shown by the imagery on the far side given that images are normally taken from an angle.

If the building has an interior courtyard the use a Multipolygon relation to ensure that the courtyard is not rendered as part of the building.

Please consider adding house numbers nodes to buildings with tags in addr:*=*-Namespace:

in JOSM

As a lot of buildings are rectangular, you can draw a rough rectangle, and then orthogonalize it in JOSM with the hotkey Q. Pressing Q on a selection sets all the angles in the selection to be 90°. Be sure you're using a projection like Mercator, otherwise if you use something like WGS84, then objects will be distorted when rendered. (Please be aware that not all buildings are orthogonal and sometimes it is better to keep an odd looking polygon instead of making a curved shape rectangular.)

JOSM/Plugins/BuildingsTools makes mapping of buildings a lot more convenient (hotkey B). This works best for buildings with four nodes.

in Potlatch

In Potlatch, you can add several buildings quickly especially in residential areas by tracing the building with one hand with the mouse and then with the other hand pressing the 'R' key to add the properties of the previously selected building. Add the source, building tag and whatever other tag you want on the first building then copy it to the other buildings.

Some ways to get the outline of the building

Observations from street level, drawing a sketch, or even taking measurements

Walking around the edge of the building taking a GPS trace. Good enough for big buildings (e.g. a stadium) but walls normally reflect the GPS signal, causing the trace to be offset a significant distance away from the building.